Explanation/Reference:
Whereas the host-to-host layer (equivalent to the OSI's transport layer) provides end-to-end data delivery service, flow control, to the application layer.
The four layers in the DoD model, from top to bottom, are:
The Application Layer contains protocols that implement user-level functions, such as mail delivery, file transfer and remote login.
The Host-to-Host Layer handles connection rendez vous, flow control, retransmission of lost data, and other generic data flow management between hosts. The mutually exclusive TCP and UDP protocols are this layer's most important members.
The Internet Layer is responsible for delivering data across a series of different physical networks that interconnect a source and destination machine. Routing protocols are most closely associated with this layer, as is the IP Protocol, the Internet's fundamental protocol.
The Network Access Layer is responsible for delivering data over the particular hardware media in use.
Different protocols are selected from this layer, depending on the type of physical network The OSI model organizes communication services into seven groups called layers. The layers are as follows:
Layer 7, The Application Layer: The application layer serves as a window for users and application processes to access network services. It handles issues such as network transparency, resource allocation, etc. This layer is not an application in itself, although some applications may perform application layer functions.
Layer 6, The Presentation Layer: The presentation layer serves as the data translator for a network. It is usually a part of an operating system and converts incoming and outgoing data from one presentation format to another. This layer is also known as syntax layer.
Layer 5, The Session Layer: The session layer establishes a communication session between processes running on different communication entities in a network and can support a message-mode data transfer. It deals with session and connection coordination.
Layer 4, The Transport Layer: The transport layer ensures that messages are delivered in the order in which they are sent and that there is no loss or duplication. It ensures complete data transfer. This layer provides an additional connection below the Session layer and assists with managing some data flow control between hosts. Data is divided into packets on the sending node, and the receiving node's Transport layer reassembles the message from packets. This layer is also responsible for error checking to guarantee error-free data delivery, and requests a retransmission if necessary. It is also responsible for sending acknowledgments of successful transmissions back to the sending host. A number of protocols run at the Transport layer, including TCP, UDP, Sequenced Packet Exchange (SPX), and NWLink.
Layer 3, The Network Layer: The network layer controls the operation of the subnet. It determines the physical path that data takes on the basis of network conditions, priority of service, and other factors. The network layer is responsible for routing and forwarding data packets.
Layer 2, The Data-Link Layer: The data-link layer is responsible for error free transfer of data frames.
This layer provides synchronization for the physical layer. ARP and RARP would be found at this layer.
Layer 1, The Physical Layer: The physical layer is responsible for packaging and transmitting data on the physical media. This layer conveys the bit stream through a network at the electrical and mechanical level.
See a great flash animation on the subject at:
http://www.maris.com/content/applets/flash/comp/fa0301.swf
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Chapter 3: Telecommunications and Network Security (page
85).
Also: HARRIS, Shon, All-In-One CISSP Certification Exam Guide, McGraw-Hill/Osborne, 2002, chapter 7:
Telecommunications and Network Security (page 344).

CHAP

Section: Risk, Response and Recovery
Explanation/Reference:
The incident response plan focuses on information security responses to incidents affecting systems and/or networks. It establishes procedures to address cyber attacks against an organization's IT systems. These procedures are designed to enable security personnel to identify, mitigate, and recover from malicious computer incidents, such as unauthorized access to a system or data, denial of service, or unauthorized changes to system hardware or software. The continuity of support plan is the same as an IT contingency plan.
It addresses IT system disruptions and establishes procedures for recovering a major application or general support system. It is not business process focused. The business continuity plan addresses business processes and provides procedures for sustaining essential business operations while recovering from a significant disruption. The continuity of operations plan addresses the subset of an organization's missions that are deemed most critical and procedures to sustain these functions at an alternate site for up to 30 days.
Source: SWANSON, Marianne, & al., National Institute of Standards and Technology (NIST), NIST Special Publication 800-34, Contingency Planning Guide for Information Technology Systems, December 2001 (page
8).

One of the key item to understand regarding backup is the archive bit. The
archive bit is used to determine what files have been backuped already. The archive bit is
set if a file is modified or a new file is created, this indicates to the backup program that it
has to be saved on the next backup. When a full backup is performed the archive bit will be
cleared indicating that the files were backup. This allows backup programs to do an
incremental or differential backup that only backs up the changes to the filesystem since
the last time the bit was cleared
Full Backup (or Reference Backup)
A Full backup will backup all the files and folders on the drive every time you run the full
backup. The archive bit is cleared on all files indicating they were all backuped.
Advantages:
All files from the selected drives and folders are backed up to one backup set.
In the event you need to restore files, they are easily restored from the single backup set.
Disadvantages:
A full backup is more time consuming than other backup options.
Full backups require more disk, tape, or network drive space.
Incremental Backup
An incremental backup provides a backup of files that have changed or are new since the
last incremental backup.
For the first incremental backup, all files in the file set are backed up (just as in a full
backup). If you use the same file set to perform a incremental backup later, only the files
that have changed are backed up. If you use the same file set for a third backup, only the
files that have changed since the second backup are backed up, and so on.
Incremental backup will clear the archive bit.
Advantages:
Backup time is faster than full backups.
Incremental backups require less disk, tape, or network drive space.
You can keep several versions of the same files on different backup sets.
Disadvantages:
In order to restore all the files, you must have all of the incremental backups available.
It may take longer to restore a specific file since you must search more than one backup
set to find the latest version of a file.
Differential Backup
A differential backup provides a backup of files that have changed since a full backup was
performed. A differential backup typically saves only the files that are different or new since
the last full backup. Together, a full backup and a differential backup include all the files on
your computer, changed and unchanged.
Differential backup do not clear the archive bits.
Advantages:
Differential backups require even less disk, tape, or network drive space than incremental
backups.
Backup time is faster than full or incremental backups.
Disadvantages:
Restoring all your files may take considerably longer since you may have to restore both
the last differential and full backup.
Restoring an individual file may take longer since you have to locate the file on either the
differential or full backup.
For more info see: http://support.microsoft.com/kb/136621
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the
Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 69.

From most effective (lowest CER) to least effective (highest CER) are: Iris scan, fingerprint, voice verification, keystroke dynamics. Reference : Shon Harris Aio v3 , Chapter-4 : Access Control , Page : 131 Also see: http://www.sans.org/reading_room/whitepapers/authentication/biometricselection-body-parts-online_139